Pressure trasmitter RS485 to DUET 2/3?



  • Hi there,
    I've got a Pressure trasmitter with a RS485 board.

    Can I read the pressure with the DUET 2 or 3?

    thanks.



  • What is the end goal? What sampling rate are you expecting to use?

    As neither a Duet 2, 3 or a 3 + Raspberry Pi have native RS485 support you would need some sort of adapter. 485 to usb or ttl are readily available, and I would think 485 to ttl on a raspberry pi would the easiest to work with ; but how to glue it together with the Duet software foundation



  • @bearer said in Pressure trasmitter RS485 to DUET 2/3?:

    What is the end goal

    To read the pressure 🙂 I have stock display on the transmitter but would like to have it read with the duet and see on the DWC (maybe?).



  • Just display it? No control loop or logic?



  • first just display.

    maybe later control loop.



  • Maybe have a think of sampling rate and response time of a control loop as it might affect the best approach.



  • RS485 tells us the physical layer that carries the data from the Pressure sensor. It does not tell us anything about that data. Is there documentation on this device?

    And, like @bearer said, what is the goal? If it is truly display only, can it be displayed as though it were a temperature sensor? Or do you literally want to add field(s) to the DWC web screens? If you are later thinking about controlling something, what might that be?

    Also, in order to type less... what is your background in Electronics? Embedded software? Web software? 3D Printing? Just a word or two...



  • @Danal

    Hey there,
    BG is mostly 3d printing and some electronics but not much.

    I'm not married to the idea of RS485. I am using pressure transmitters for my setup, they have various outputs, so I'm wondering if it can be connected to the DUET for just reading the signal. If possible to have it part of some logic, that would be cool.

    I've attached a spec sheet of the pressure transmitter PCM350 (WTR02) Sanitary Flush Pressure Transmitter :V1.1.pdf

    outputs:
    B1: 4~20mA
    B2: 1~5V
    B3: 0~5V
    B6: 0.5~4.5V
    B7: 0~10V

    the transmitter can come with a dedicated display, thats not a problem. just thought it would be good to have it display in the DWC.

    any thoughts?



  • I would look into interfacing any of the analouge signals to a thermistor input, and create a virtual heater with suitable constants for showing pressure instead of temperature (but it would still show as a temperature unit)



  • From the datasheet, the device itself can output voltage or current, to drive gauges and displays. Since it is already driving a dedicated display, do we know what mode it uses?

    I'm think of the sensor/display as a "unit", and monitoring the voltage (or current) via a small processor (Arduino or similar for one off, attiny for dozens to thousands) that in turn interfaces to the Duet. Probably on one of the Duet's temperature interfaces, so that the numbers "just display" on the DWC fields that already exist (as bearer suggested above).

    There is probably a way to directly interface... but I'd be very reluctant to wire a device that may be putting out 5V or 10V (the datasheet is a little unclear) directly to the processor on a duet. Too much chance of blowing an expensive board. I'd much rather blow a pin on a $10 arduino.


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